Well, i definately don't think you will have a problem with an overcrowded volcano pool in Oct. -We were there in Nov, and it was fine. Yes, it is not a HUGE pool, but it is very adaquate.
You didn't say how old your kids are -- this will affect your decision too.. As should what parks you want to concentrate on.
SAB is by far the best pool on WDW property, but it is a big area. However, i disagree with the above poster (respectfully)

As we stayed at the BC when my dd was 3,4,& 5 -- and i love the smaller pool at SAB for her, i love the fact that it is distinctly separate from the bigger pool area, but yet, feels connected..and it was VERY easy to see my dd in the smaller pool.. and the sand there is wonderful touch -- there is usally someone there building sandcastles with the kids too. My dd LOVES this pool -- however, this november, she will be 7, and is a really good swimmer, so i am sure she will want to be in the bigger part too -- which is fine.
So,i definately would not suggest picking a pool just on the zero entry thing!!
As i said, it would help if i new the ages of your kids.
Also -- if you plan on going to the MK alot - the access to the monorail is wonderful from the poly (or the quick boat ride), but if you will be at Epcot, or Disney Holly.studios - then the BC would be the better choice.